Me and my friend have figured out that the Original Crayola markers work very good because they are just small enough to fit the barrel but seal good enough to stay in <b>without</b> using a wad of paper. Any marker that is the same size like Roseart will also work. The Roseart packs of 11 are roughly $2.00 at Wal Mart while the Crayolas are almost $3.00